DESC:CROSS-REFERENCE TO RELATED APPLICATIONS
[001] This application is based on and derives the benefit of Indian Provisional Application 201721011831, the contents of which are incorporated herein by reference.
TECHNICAL FIELD
[002] The embodiments herein generally relate to power transmission unit and more particularly, but not exclusively to a synchronizer assembly for a power transmission unit of a vehicle, a machine and the like.
BACKGROUND
[003] The off-highway vehicle(s) like tractor(s) or similar vehicle(s) is used in the field of agricultural, construction and material handling for different operations and/or purposes. The nature of work being carried out by these types of vehicles requires the vehicles to be operated frequently in both forward and reverse direction having equal speed range. In an industrial vehicle equipped with a conventional manual shift transmission, a series of operations must be carried out to achieve the rapid forward/reverse shifting of the drive mode. Therefore, sometimes, the transmission is damaged by forced forward/reverse shifting operation at a running speed where shift-down and forward/reverse shift are impossible. In a vehicle equipped with a manual transmission, the series of such intricate operations requires a high-level operating skill. On the other hand, various vehicles including industrial vehicles, such as fork lift trucks, equipped with a synchronizer unit have been proposed in recent years.
[004] Generally, a synchronizer unit in a power transmission unit (gear box assembly) of a vehicle is used for gradual engagement or dis-engagement of corresponding gears in the power transmission unit. Synchronizer units are used in the power transmission unit (gear box assembly) for ease of gear shifting and to enhance life of meshing gears, as a control shifting ring (part of synchronizer) shifts only after speed difference between two gears is minimized or zero with the help of friction element. The synchronizer unit, which is used for increasing the life of meshing gears, fails if its assembly which requires precise centralization with the help of graded spacers on both the sides of synchronizer unit is not done properly. The graded spacer on both sides of the synchronizer unit is selected by a hit and trial method to centralize it. There is a high chance of incorrect centralization, which goes undetected at the time of assembly and results in reduced efficiency of power transmission unit and results in failure of the synchronizer unit. Variations in selection of graded spacers leads to incorrect centralization with respect to shifter fork, generating unintended shifting force, making a friction element work continuously to reduce the gear speed, ultimately resulting in overheating and burning of the synchronizer, and groove formation on hub. Also heat generation due to friction element, reduces the efficiency of the power transmission unit.
[005] Therefore, there exists a need for a synchronizer assembly for a power transmission unit, which obviates the aforementioned drawbacks.
OBJECTS
[006] The principal object of an embodiment of this invention is to provide a synchronizer assembly for a power transmission unit for a vehicle, a machine and the like.
[007] Another object of an embodiment of this invention is to provide a synchronizer assembly for a forward/reverse change over unit in existing transmission system of a vehicle for producing equal number of reverse speeds that of available forward speeds, thereby minimizing development time and cost by avoiding re-designing of existing transmission system.
[008] Yet another object of an embodiment of this invention is to provide a synchronizer assembly which improves productivity, having low failures and reduction in efforts.
[009] These and other objects of the embodiments herein will be better appreciated and understood when considered in conjunction with the following description and the accompanying drawings. It should be understood, however, that the following descriptions, while indicating embodiments and numerous specific details thereof, are given by way of illustration and not of limitation. Many changes and modifications may be made within the scope of the embodiments herein without departing from the spirit thereof, and the embodiments herein include all such modifications.
BRIEF DESCRIPTION OF DRAWINGS
[0010] The embodiments of the invention are illustrated in the accompanying drawings, throughout which like reference letters indicate corresponding parts in the various figures. The embodiments herein will be better understood from the following description with reference to the drawings, in which:
[0011] FIG. 1a depicts a cross-sectional view of a synchronizer assembly for a power transmission unit, according to an embodiment of the invention as disclosed herein;
[0012] FIG. 1b depicts a cross-sectional view of a synchronizer assembly for a power transmission unit along with shifting mechanism, according to an embodiment of the invention as disclosed herein; and
[0013] FIG. 2 depicts of flow chart of a method of providing a synchronizer assembly 100 for a power transmission unit for a vehicle, according to an embodiment of the invention as disclosed herein.

DETAILED DESCRIPTION
[0014] The embodiments herein and the various features and advantageous details thereof are explained more fully with reference to the non-limiting embodiments that are illustrated in the accompanying drawings and detailed in the following description. Descriptions of well-known components and processing techniques are omitted so as to not unnecessarily obscure the embodiments herein. The examples used herein are intended merely to facilitate an understanding of ways in which the embodiments herein may be practiced and to further enable those of skill in the art to practice the embodiments herein. Accordingly, the examples should not be construed as limiting the scope of the embodiments herein.
[0015] The embodiments herein achieve a synchronizer assembly for a power transmission unit for a vehicle, a machine and the like. Further the embodiments herein achieve a synchronizer assembly for a forward/reverse changeover unit in existing transmission system of a vehicle for producing equal number of reverse speeds that of available forward speeds, thereby minimizing development time and cost by avoiding re-designing of existing transmission system. Referring now to the drawing, and more particularly to FIGS. 1 and 2, where similar reference characters denote corresponding features consistently throughout the figures, there are shown embodiments.
[0016] FIG. 1a depicts a cross-sectional view of a synchronizer assembly for a power transmission unit, according to an embodiment of the invention as disclosed herein. In an embodiment, the synchronizer assembly for the power transmission unit includes a housing 102, an input shaft 104, a first bearing 106a, a second bearing 106b, a synchronizer pack 108, a rear drive shaft 110, an input gear 112, a synchronizer hub 116, at least one sleeve 118, an output gear 120, an idler gear 122, a first cluster gear 124, a shaft 126, a second cluster gear 128, a plurality of needle roller bearing 130, at least one axial thrust bearing 132, at least two thrust washers 134, at least one graded spacer 136, and a end cover 138.
[0017] The synchronizer assembly 100 for the power transmission unit includes the housing 102. The housing 102 includes a first end (not shown) and a second end (not shown). The synchronizer assembly 100 further includes further includes an end cover 138. The end cover 138 is disposed at first end of the housing 102. The end cover 138 acts as retainer for the synchronizer assembly 100. The housing 102 covers encloses the synchronizer sub-assembly. The housing 102 is positioned in between an engine and a transmission system of a vehicle. The power from the engine of the vehicle through a clutch assembly (not shown) mounted on an engine flywheel (not shown) is supplied to a main drive shaft (not shown). The main drive shaft further meshes with the input shaft 104. The main drive shaft includes a plurality of splines which meshes internally with a plurality of gear teeth defined in the input shaft 104. The input shaft 104 is configured to be a hollow input shaft (hereafter referred as hollow input shaft). The hollow input shaft 104 includes a first end (not shown) and a second end (not shown). The first end of the hollow input shaft 104 includes a collar. The second end of the hollow input shaft 104 is disposed in the housing 102 using a first bearing 106a. Further the hollow input shaft 104 is connected to the forward/reverse sub assembly 108 (hereafter referred as synchronizer pack 108). The hollow input shaft 104 acts as an input to the synchronizer pack 108. The synchronizer pack 108 includes a first end (not shown) and a second end (not shown). The input gear 112 is disposed adjacent to the synchronizer pack 108 at first end and output gear 102 is disposed at the second end of the synchronizer pack 108.
[0018] Further the synchronizer assembly 100 for the power transmission unit includes the forward/reverse fork unit (not shown). The fork unit is configured to move the synchronizer pack 108 in first direction or in a second direction to select forward rotation motion or the reverse rotation motion by means of mechanical shifting components. The fork unit is operated by a direction control lever (not shown) and mechanical shifting components are coupled to the synchronizer pack 108.
[0019] The power from the synchronizer pack 108 is supplied to the rear drive shaft 110 disposed at second end of the housing 102. The rear drive shaft 110 is mounted on second bearing 106b. Based on the selection of the first direction or the second direction of the synchronizer pack 108 the rear drive shaft 110 is rotated in forward rotation motion or clockwise direction and the reverse rotation motion or anti-clockwise direction respectively.
[0020] The hollow input shaft 104 further includes a plurality of external splines (not shown) which is meshed with a plurality of splines defined in the synchronizer hub 116. The rotational motion of the hollow input shaft 104 is transferred to the synchronizer hub 116 which further rotates the synchronizer pack 108. The synchronizer pack 108 includes at least one sleeve 118 which is rotated by the synchronizer hub 116. The sleeve 118 meshes with the fork unit of the synchronizer assembly 100. The fork unit is configured to move the synchronizer pack 108 in first direction or in a second direction to select forward rotation motion or the reverse rotation motion.
[0021] The synchronizer pack 108 is configured to move in first direction to provide forward rotation motion. The motion of the synchronizer pack 108 in the first direction causes the synchronizer hub 116 to rotate the output gear 120. The output gear 120 internally meshes with the rear drive shaft 110. The output gear 120 includes a plurality of splines (not shown) which meshes with gear teeth (not shown) of the rear drive shaft 110.
[0022] FIG. 1b depicts a cross-sectional view of a synchronizer assembly for a power transmission unit along with shifting mechanism, according to an embodiment of the invention as disclosed herein. The synchronizer pack 108 is configured to move in second direction to provide reverse rotation motion. The motion of the synchronizer pack 108 in the second direction causes the synchronizer hub 116 to rotate the input gear 112. The input gear 112 is further meshed with the idler gear 122. The input gear 112 is mounted on a plurality of needle roller bearing 130. As the input gear 112 moves in relative motion with respect to the hollow input shaft 104, the plurality of needle roller bearing 130 is provided between them to facilitate easy rotation of the input gear 112 without interrupting the rotation of the hollow input shaft 104. The idler gear 122 further meshes with the first cluster gear 124 mounted on the shaft 126 at first end (not shown). Further the shaft 126 includes the second cluster gear 128 mounted at the second end (not shown). The second cluster gear 128 is further meshed with the output gear 120. The output gear 120 internally meshes with the rear drive shaft 110. The direction of rotation of the input hollow shaft 104 is reversed by moving the synchronizer pack 108 in the second direction.
[0023] The synchronizer assembly 100 further includes at least one axial thrust bearing 132 and at least two thrust washers 134. The axial thrust bearing 132 and the thrust washers 134 are stacked between the output gear 120 and the synchronizer hub 116. As the output gear 120 moves in relative motion with respect to the synchronizer hub 116, the axial thrust bearing 132 and the thrust washers 134is provided between the output gear 120 and the synchronizer hub 116to facilitate easy rotation of the output gear 120 without interrupting the rotation of the synchronizer hub 116 as the output gear 120 and the synchronizer hub 116 may rotate in opposite directions.
[0024] The synchronizer assembly 100 further includes at least one graded spacer 136 disposed adjacent to the output gear 120. The graded spacer 136 is mounted between the output gear 120 and the second bearing 106b. The graded spacer 136 is configured to centralize the synchronizer pack 108. The graded spacer 136 facilitates in moving the sleeve 118 to align with the fork unit. For example, the graded spacers may be selected from the spacers ranging from 5.2, 5.3, 5.4, 5.5 and so on.
[0025] FIG. 2 depicts of flow chart of a method of providing a synchronizer assembly 100 for a power transmission unit for a vehicle, according to an embodiment of the invention as disclosed herein. A method 200 of providing a synchronizer assembly 100 for a power transmission unit for a vehicle is provided. At step 202, the method includes providing a housing 102 having a first end and a second end. At step 204, the method includes mounting an input shaft 104 at first end of the housing 102. At step 206, the method includes mounting a synchronizer pack 108 in said housing 102, said synchronizer pack 108 having a first end and a second end, said synchronizer pack 108 in communication with said input shaft 104, said synchronizer pack 108 configured to move in at least one of a first direction and a second direction. At step 208, the method includes coupling a fork unit to said synchronizer pack 108 to move said synchronizer pack 108 in at least one of the first direction and the second direction. At step 210, the method includes disposing an input gear 112 adjacent to synchronizer pack 108 at first end to selectively couple with synchronizer pack 108. At step 212, the method includes disposing an output gear 120 adjacent to synchronizer pack 108 at second end to selectively couple with synchronizer pack 108. At step 214, the method includes coupling a rear drive shaft 110 to said output gear 120. At step 216, the method includes disposing at least one axial thrust bearing 132 between the output gear 120 and the synchronizer pack 108. At step 218, the method disposing at least two thrust washers 134 on both sides of the axial thrust bearing 132. The synchronizer pack 108 is configured to move in first direction to couple with the output gear 120 to rotate the rear drive shaft 110 in clockwise direction. The synchronizer pack 108 is configured to move in second direction to couple with the input gear 112 to rotate the rear drive shaft 110 in anti-clockwise direction.
[0026] The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments herein have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.
,CLAIMS:We claim,
1. A synchronizer assembly 100 for a power transmission unit for a vehicle, the assembly 100 comprising:
a housing 102 having a first end and a second end;
an input shaft 104 mounted at first end of said housing 102;
a synchronizer pack 108mounted in said housing 102, said synchronizer pack 108having a first end and a second end, said synchronizer pack 108in communication with said input shaft 104, said synchronizer pack 108 configured to move in at least one of a first direction and a second direction;
a fork unit coupled to said synchronizer pack 108 to move said synchronizer pack 108 in at least one of said first direction and said second direction;
an input gear 112 disposed adjacent to synchronizer pack 108at first end to selectively couple with synchronizer pack 108;
an output gear 120 disposed adjacent to synchronizer pack 108at second end to selectively couple with synchronizer pack 108;
a rear drive shaft 110 coupled to said output gear 120;
at least one axial thrust bearing 132 disposed between said output gear 120 and said synchronizer pack 108;
at least two thrust washers 134 disposed on both sides of said axial thrust bearing 132,
wherein
said synchronizer pack 108 is configured to move in first direction to couple with said output gear 120 to rotate said rear drive shaft 110 in clockwise direction; and
said synchronizer pack 108 is configured to move in second direction to couple with said input gear 112 to rotate said rear drive shaft 110 in anti-clockwise direction.

2. The synchronizer assembly 100 as claimed in claim 1, wherein said input shaft 104 is configured to be hollow.

3. The synchronizer assembly 100 as claimed in claim 1, wherein said input shaft 104 includes:
a first end having a collar; and
a second end disposed in said housing 102 through a first bearing 106a.

4. The synchronizer assembly 100 as claimed in claim 1, wherein said synchronizer assembly 100 further includes at least one graded spacer 136 mounted between said output gear 120 and said second bearing 106b.

5. The synchronizer assembly 100 as claimed in claim 1, wherein said input shaft 104 is meshed with an idler gear 122 for rotating said rear drive shaft 110 in anti-clockwise direction.

6. A method 200 of providing a synchronizer assembly 100 for a power transmission unit for a vehicle, said assembly 100 comprising:
providing a housing 102 having a first end and a second end;
mounting an input shaft 104 at first end of said housing 102;
mounting a synchronizer pack 108in said housing 102, said synchronizer pack 108 having a first end and a second end, said synchronizer pack 108 in communication with said input shaft 104, said synchronizer pack 108 configured to move in at least one of a first direction and a second direction;
coupling a fork unit to said synchronizer pack 108 to move said synchronizer pack 108 in at least one of said first direction and said second direction;
disposing an input gear 112 adjacent to synchronizer pack 108 at first end to selectively couple with synchronizer pack 108;
disposing an output gear 120 adjacent to synchronizer pack 108 at second end to selectively couple with synchronizer pack 108;
coupling a rear drive shaft 110 to said output gear 120;
disposing at least one axial thrust bearing 132 between said output gear 120 and said synchronizer pack 108;
disposing at least two thrust washers 134 on both sides of said axial thrust bearing 132,
wherein
said synchronizer pack 108 is configured to move in first direction to couple with said output gear 120 to rotate said rear drive shaft 110 in clockwise direction; and
said synchronizer pack 108 is configured to move in second direction to couple with said input gear 112 to rotate said rear drive shaft 110 in anti-clockwise direction.